1. Field of the Invention
The present invention relates to a hemming device and a hemming method for hemming a plate-like workpiece.
2. Description of Related Art
Conventionally, while the inner panel and the outer panel, for example, of a rear door which are the panel members of a vehicle are assembled with each other, hemming for hemming the peripheral edge of the outer panel and superposing the hemmed peripheral edge thereof on the peripheral edge of the inner panel is carried out by a hemming device shown in FIG. 1 which is a side view of the hemming device and in FIG. 2 which is a plan view thereof.
In this hemming device, a workpiece W is positioned and set on a hemi die 3 disposed on a base 1 in a state in which the outer panel 5 is provided below an inner panel 7. The inner panel 7 is positioned and fixedly positioned on this upper position by a positioning jig 9 which is vertically moved by a cylinder 8. The workpiece W thus positioned is provisionally hemmed by a plurality of pre-hemming punches 11 provided around the workpiece W and then finally hemmed by hemming punches 13 provided to correspond to the respective pre-hemming punches 11.
The hemming punches 13 and the pre-hemming punches 11 are actuated by hydraulic cylinders 19 rotatably supported by brackets 15 fixed to the base 1 through rotation support shafts 17, respectively. That is to say, if the hydraulic cylinder 19 is driven, the piston rode 21 of the cylinder 19 advances and a punch holder 23 having hemming punches 13 on a tip end thereof rotates about a rotation support shaft 27 in an arrow A direction relative to the bracket 25 on the base 1, whereby the final hemming is carried out by the hemming punches 13.
On the other hand, the pre-hemming punches 11 carry out provisional hemming prior to the hemming by the hemming punches 13 by advancing to the workpiece W by the rotational operation of the punch holder 23 in the arrow A direction and then retreat. That is to say, using one hydraulic cylinder 19, the provisional hemming by the pre-hemming punches 11 and the final hemming by the hemming punches 13 are carried out in succession.
As for working units Us and Uc each consisting of the hemming punch 13, the pre-hemming punch 11, the hydraulic cylinder 19 driving the respective punches and the like, a total of eight, i.e., four working units (Us) corresponding to the linear portion of a generally rectangular rear door and four working units (Uc) corresponding to the corner portions of the rear door, are provided so as to hem the entire periphery of the workpiece W as shown in FIG. 2.